1. Technical Field
Various embodiments relate generally to a semiconductor device and, more particularly, to a three-dimensional semiconductor device.
2. Related Art
Non-volatile memory devices can retain the stored data regardless of power on/off conditions. As memory devices having memory cells fabricated in the form of a single layer on silicon substrates have reached physical limits in increasing the degree of integration, there are proposals of three-dimensional (3D) structured non-volatile memory devices that have memory cells vertically stacked on silicon substrates.
A 3D non-volatile memory device may include interlayer insulating layers and word lines stacked alternately with each other and channel layers penetrating therethrough. In addition, memory cells may be stacked along the channel layers. The degree of integration of the 3D non-volatile memory device having the above-described configuration may be improved by arranging strings in a U shape.
However, since the stacked memory cells are formed at the same time, there is a limit in increasing the thickness of the stacked word lines. Therefore, each of the word lines may have a high resistance. In addition, since a memory layer of the memory cells and a gate insulating layer of a pipe transistor include the same materials, the gate insulating layer may not be thick enough. Therefore, a threshold voltage of the pipe transistor may vary. As a result, it may be difficult to ensure characteristics of the 3D non-volatile memory device.